Casing bit with a removable center



Jan. 14, 1964 J. L. WILCOX EIAL 3,117,636

CASING BIT WITH A REMOVABLE CENTER Filed June 8, 1960 3 Sheets-Sheet 1 1964 J- L. WILCOX ETA]. 3,117,636

CASING BIT WITH A REMOVABLE CENTER Filed June 8, 1960 FM Y 3 Sheets-Sheet 2 as so 68 John L. Wilcox John J. Jensen INVENTORS 72 Jan. 14, 1964 J. L. WILCOX E'rAL 3,117,636

CASING BIT WITH A REMOVABLE CENTER Filed June 8, 1960 3 Sheets-Sheet 5 WET IT! Fig. 4

John L. W/Ycox John J, Jensen INVENTORS BY WW 3m United States Patent 3,117,636 CASING BET WlTH A REMGVABLE CENTER John L. Wilcox and Eohn J. Jensen, both or R0. Box 569, McMinnville, Greg. Filed .l'uue 8, 1960, Ser. No. 34,768 Claims. (Cl. 175-257) This invention comprises a novel and useful casing bit with a removable center and more particularly pertains to a novel bit adapted to be connected to a casing section to assist in setting the casing and having a removable center through which a core barrel or drill can be passed through the casing bit to obtain core samples.

It is frequently desirable to obtain core samples from or drill conventionally in a formation in which it is necessary to first drill a borehole through an overburden of a relatively loose or unconsolidated material which tends to crumble and fall into the borehole. To overcome this difficulty, the common practice is to install a string of steel casing through the overburden to prevent the Wall of the bore from caving in and blocking further operations. However, after the bore has been drilled into the desired formation from which it is desired to take core samples, a difficulty arises in the operation of inserting or introducing a core drill through the casing string to perform the coring operation.

It is therefore the primary purpose of this invention to provide an apparatus and a means to overcome the foregoing diflculty and to enable a coring or drilling operation of any character to be satisfactorily performed despite the passage of the bore through an overburden having a tendency to cave into the bore.

A further object of the invention is to provide a means whereby the casing itself may be provided with a drill bit to facilitate the introduction of the casing through the overburden down to the desired formation to be cored together with means facilitating the operating of a coring drill once the casing and its drill bit have been placed in the desired position for corin Yet another object or" the invention is to provide an apparatus and a means whereby the casing string may be provided with a drill bit on the lower end thereof to facilitate the insertion of the casing string to any desired position, which bit shall include an outer portion relatively fixedly secured to the casing and an inner portion which may be removed from the interior of the casing string after the casing string has been put in the proper posi tion to thereby provide a passageway through the center of the casing bit through which the core drill may be inserted and operated.

Still another object of the invention is to provide an apparatus and a method whereby a casing with a drill bit secured thereto may be effectively placed into the desired position with respect to a formation to be cored; the central portion of the drill bit may be removed and a coring or conventional drill operated therethrough to effect the desired coring or drilling operation; and whereby after the coring or drilling operation has been finished the drill, coring drill and its barrel may be recovered through the casing string and the casing string itself with too casing bit thereon may likewise be recovered.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a fragmentary View in vertical central section through a portion of a formation illustrating the manner in which the present invention is applied to a casing string and is operated to effect the positioning of the latter in proper relation to a formation to be cored;

FIGURE 2 is a view similar to FIGURE 1 but showing the manner in which the central portion of the casing drill bit is removed in order to permit the use of a coring drill therethrough;

FIGURE 3 is an enlarged View in vertical central section through the lower end of the casing string showing the casing bit attached thereto togther with the removable central portion of the casing bit and the means for detachably mounting the latter upon the casing drill bit;

FIGURE 4 is a view in elevation, parts being broken away and shown in vertical section, of a somewhat modified construction of casing bit with a relatively fixed outer portion and a removable center portion; and

FIGURE 5 is a bott n1 plan view of the bit or" FlG- URE 4.

Referring first to FlGURES l and 2 it will be seen that the numeral 1% designates an overburden through which a bore 12 must be drilled in order to obtain access to a formation 14 from whi h it is desires to take a series of core samples. The overburden is of a character which will readily crumble, collapse or cave into the bore 12 so as to hnpose difiiculties in the operation of a coring drill if the well bore is not cased.

Shown at 15 is a conventional string of easing which is to be set in the overburden 1b and down into contact with the formation 14 in order to prevent caving of the overburden it into the well bore.

Referring now and in particular to FlGUlZE 3 it will be observed that the lower section of the casing string 16 has secured to the exterior thereof a drill bit in the usual manner. This drill bit is hollow, and at the lower end thereof is provided with the usual drill teeth 25?. The bit is of such size that when mounted upon the casing string the entire casing string may be rotated and thus consti ute a drilling string whereby the casing string will be caused to bore its way through the overburden 1% until the drill bit 2% is in contact with the formation 14 to be cored. As will be understood, during this operation the presence of the casing string prevents the ingress of the overburden or other foreign matter into the bore during this operation.

The drill bit 13 which is attached to the end of the casing string in accordance with this invention is of a particular construction. Thus, at tirelower end of the drill bit and extending upwardly therefrom into about th midportion of the bit or higher if desired is an axial bore 22. At the upper end, this bore is provided with an upwardly and outwardly flaring portion which is internally threaded and which at the upper end thereof terminates in an annular shoulder surface or shoulder as which is perpendicular to the 10 'tudinal axis of the drill bit. Rising from the outer penmeter of the shoulder 26 is the internally threaded portion 23 by wlL'ch the drill bit is secured to the exterior of the casing 16. It will thus be seen that as so far described a continuous passageway is provided from the interior of the casing through the drill bit 18 by means of the bores 24 and 22.

Removably seated in the threaded bore 24 is an internal connector sub 3:). This latter consists of an elongated body having a diametrically enlarged upper portion 32 provided with an annular shoulder 34 on its lower face which mates with and abuts against the shoulder 26 of the drill bit 1%. The upper surface of the portion 32 is provided with a conical dish-shaped surface 36 from the central portion of which extends downwardly an axial bore 33 so that the surface 36 constitutes a guide surface to direct a drill string into this bore as hereinafter set forth. The bore 33 itself is provid d with a series of right hand threads as.

Depending from the upper portion 32, the body 3% has a downwardly tapering main portion 52 whose external surface is threaded to engage with the threads 24-. The

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threaded engagement of the portion 42 with the threads 24 is by means of a left hand thread for a purpse to be subsequently apparent.

Depending from the threaded portion 40 of the bore 33 is a diametrically reduced axial bore 4 which extends entirely to the lower face of the internal sub 3%. The lower portion of the body 39 is cylindrical in shape as shown at 46 and is provided with a conical upwardly convergent bore 43 provided therein with right hand internal threads 5% and at its upper end terminating in an annular flat shoulder 52. As will be observed, the exterior surface of he cylindrical lower portion 46 is spaced rrom the adjacent walls of the bore 22 to provide an annular clearance therebe.ween and a plurality of drilling fluid circulating passages as at 54 communicating this space with the interior of the bore 44.

Secured to, carried by and depending from the cylindrical portion 46 or" the internal sub 34} is a center drill bit This latter has a bore 62 opening upwardly from the botom surface thereof which bore merges into a diametrically reduced bore d4 which when the parts are assembled forms a continuation of the bore 44. Rising bove the lower portion of the bit 6t is an upwardly convergent conical extension 625 having external threads thereon which engage with the threads 58. This threaded engagement is a right hand thread for a purpose to be subsequently apparent. At its upper end, the tapering conical portion 66 has a flat annular top surface 79 which is slightly spaced from the surface 52 previously mentioned.

Drill teeth or drilling elements of any desired character are secured to and carried by the drill bit 6d at its lower end. illustrated are types of rotary cutters '72 although it be understood that any desired types of cutters can be employed.

With removable center bit at assembled in position as shown in FEGURE 3 in the main composite bit assembly 18, there is provided a bit extending across the entire cross-sectional area of the casing to effectively penetrate the overburden ill during rotation of the casing to thereby cause the casing to penetrate through the same and as shown in FIGURES l and 2 seat upon the formation 14 which is to be cored. During this operation drill fluid can be circulated by means of a fiuid supply to the bore 38 and through the bore 44 and ducts 54 to the annular space between the inner removable drill bit and the outer bit 13. The entire device as shown in FIGURE 3 operates as a unit upon rotation of the casing which in turn drives the bit 13 and through engagement with the latter by the threaded engagement 24 drives the internal sub 3%) and the inner removable drill bit 6% carried thereby. Thus the casing is readily drilled fnrough the overburden 1'9 and to the desired position relative to the formation to be cored.

After the casing has been installed in the position shown in FIGURES l and 2, and is ready to begin the coring operation, it is merely necessary to introduce a drilling string or the like 78, and engage the same in the threads of the bore 33, if the drilling string is not already in place. Thereupon the drilling string can be rotated in a reverse direction in which the drilling string will be firmly secured to the internal sub 3% and will thus disconnect this sub at the threaded engagement 24 from the outer portion of the drill bit 1% so that the inner sub carrying with it the removable inner bit 61 may be withdrawn through the casing string to the surface. This operation is effected by virtue of the clearance between the outer circumference of the upper portion 32 of the inner sub and the internal Wall of the casing 16, the tapering connection between the portion 42 of the sub and the threaded bore of the upper end of the bit 1%, and the annular clearance between the cylindrical bore portion 46 of the sub, and the exterior surface of the inner drill bit 66 with the bore 22.

After the internal sub and removable inner bit have been withdrawn as a unit from the outer portion of the casing bit 18, a conventional coring drill may be attached to a drilling string inserted through the casing, past through the bore 22 and perform its coring operations. After the desired core samples have been obtained, and it is desired to withdraw from the hole, the coring drill may be first Withdrawn and thereafter the casing may be pulled. Thus there is considerable saving in the time required both to eilect the coring operation after a casing has been inserted and seated adjacent the formation to be cored as Well as in the coring operation itself and the withdrawal of the coring tool and/ or the casing string.

The construction of FIGURES 4 and 5 is identical to that of FEGURE 3 except that an outer bit 38 is provided with a different type of bit teeth, there being shown thus roller bits 8% carried by the head portion S2 of tne outer bit 18 as well as by the removable inner bit fill previously mentioned. Obviously different types of bits can be employed for different types of formations to be cored or drilled.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A drill bit which comprises a body member having an aperture formed centrally therein, said aperture having upper and lower portions, cutting means secured to said body member at one end thereof, means formed on the opposite end of said body member for securing casing thereto, a sub located within the aperture formed in said body member, said sub having an aperture formed axially therein and a lower portion of said sub being of reduced cross section to form an annulus between said body member and said portion of the sub, means formed at the upper portion of said aperture in said body member for releasably securing said sub to said body member, means in the upper portion of said sub for securing a drill stem thereto for removal of said sub from said body member, an interior cutting tool secured to the lower end of said sub, said tool having an axial bore formed therein in communication with said aperture in the sub, at least a portion of said cutting tool extending into the aperture formed in the body member to form an annulus therein in communication with the annulus formed between said body member and the lower portion of the sub, and a duct in communication with said annulus and with the aperture in said sub and with the bore of said cutting tool.

2. The bit defined in claim 1 wherein the means for releasably securing the sub to said body member comprises left hand threads and wherein the means for securing a drill stem to said sub comprises right hand threads.

3. The bit defined in claim 2 wherein a drill stem guide is formed in the upper portion of said sub.

4. The bit defined in claim 3 wherein said guide comprises a frusto-conical depression.

5. The bit defined in claim 4 wherein the upper portion of the aperture formed in said body member is tapered downwardly.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A DRILL BIT WHICH COMPRISES A BODY MEMBER HAVING AN APERTURE FORMED CENTRALLY THEREIN, SAID APERTURE HAVING UPPER AND LOWER PORTIONS, CUTTING MEANS SECURED TO SAID BODY MEMBER AT ONE END THEREOF, MEANS FORMED ON THE OPPOSITE END OF SAID BODY MEMBER FOR SECURING CASING THERETO, A SUB LOCATED WITHIN THE APERTURE FORMED IN SAID BODY MEMBER, SAID SUB HAVING AN APERTURE FORMED AXIALLY THEREIN AND A LOWER PORTION OF SAID SUB BEING OF REDUCED CROSS SECTION TO FORM AN ANNULUS BETWEEN SAID BODY MEMBER AND SAID PORTION OF THE SUB, MEANS FORMED AT THE UPPER PORTION OF SAID APERTURE IN SAID BODY MEMBER FOR RELEASABLY SECURING SAID SUB TO SAID BODY MEMBER, MEANS IN THE UPPER PORTION OF SAID SUB FOR SECURING A DRILL STEM THERETO FOR REMOVAL OF SAID SUB FROM SAID BODY MEMBER, AN INTERIOR CUTTING TOOL SECURED TO THE LOWER END OF SAID SUB, SAID TOOL HAVING AN AXIAL BORE FORMED THEREIN IN COMMUNICATION WITH SAID APERTURE IN THE SUB, AT LEAST A PORTION OF SAID CUTTING TOOL EXTENDING INTO THE APERTURE FORMED IN 